Steel material and method for its manufacturing

Abstract

A steel material which is manufactured in a non-powder metallurgical way, comprising production of ingots or castings from a melt, consists of an alloy having the following chemical composition in weight-% Carbon: 2.0-4.3%, Silicon: 0.1-2.0%, Manganese: 0.1-2.0%, Chromium: 5.6-8.5%, Nickel: max. 1.0%, Molybdenum: 1.7-3%, wherein Mo completely or partly can be replaced by double the amount of W, Niobium: max. 2.0%, Vanadium: 6.5-15%, wherein V partly can be replaced by double amount of Nb up to max. 2% Nb, Nitrogen: max. 0.3%, wherein the contents of on the one hand carbon and nitrogen and on the other hand vanadium and any possibly existing niobium shall be balanced relative to each other, such that the contents of the said elements shall lie within the area of A, B″, E, F, B′, B, C, D, A in the co-ordinate system in FIG. 2, where V+2Nb, C+N co-ordinates for said points are A: (9,3.1), B″: (9,2.85), E: (15,4.3), F: (15,3.75), B′: (9,2.65), B: (9,2.5), C: (6.5,2.0), D: (6.5,2.45).

We claim:  
     
       1. Steel material, which is manufactured in a non-powder metallurgical way, comprising manufacture of ingots or castings from a melt, characterised in that the material consists of an alloy having the following chemical composition in weight-%: 
       
         
           
                 
                 
               
                     
                 
                   Carbon: 
                   2.0-4.3% 
                 
                   Silicon: 
                   0.1-2.0% 
                 
                   Manganese: 
                   0.1-2.0% 
                 
                   Chromium: 
                   5.6-8.5% 
                 
                   Nickel: 
                   max 1.0% 
                 
                   Molybdenum: 
                   1.7-3%, wherein Mo completely or partly can be 
                 
                     
                   replaced by double the amount of W 
                 
                   Niobium: 
                   max 2.0% 
                 
                   Vanadium: 
                   6.5-15%, wherein V partly can be replaced by the double 
                 
                     
                   amount of Nb up to max 2% Nb 
                 
                   Nitrogen: 
                   max 0.3% 
                 
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       wherein the contents of on one hand carbon and nitrogen and on the other hand vanadium and any possibly existing niobium shall be balanced relative to each other, such that the contents of the said elements shall lie within the area of A, B″, E, F, B′, B, C, D, A in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       A: 9,3.1  
       B″: 9,2.85  
       E: 15,4.3  
       F: 15,3.75  
       B′: 9,2.65  
       B: 9,2.5  
       C: 6.5,2.0  
       D: 6.5,2.45,  
       balance essentially only iron and impurities and that the material at room temperature, after hardening and tempering, has a hardness between 55 and 66 HRC and a micro-structure consisting of a matrix, which substantially consists of martensite and, in said matrix, 10-40 vol.-% of hard particles of MX type, where M is vanadium and/or niobium, and X is carbon and/or nitrogen, said hardness and structure being obtainable through the non-powder metallurgical method of manufacture and through heating of the material to a temperature between 900° C. and 1150° C., through-heating of the material at said temperature during a period of time of 15 min to 2 h, cooling the material to room temperature and tempering it once or several times at a temperature of 150-650° C. 
     
     
       2. Steel material according to  claim 1 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area A, B, C, D, A in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       A: 9,3.1  
       B: 9,2.5  
       C: 6.5,2.0  
       D: 6.5,2.45  
       wherein said matrix contains 10-25 vol.-% of hard particles of MX type. 
     
     
       3. Steel material according to  claim 2 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area A, B′, C′, D′, A in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       A: 9,3.1  
       B′: 9,2.65  
       C′: 6.5,2.1  
       D: 6.5,2.45.  
     
     
       4. Steel material according to  claim 2 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area A, B″, C″, D, A in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       A: 9,3.1  
       B″: 9,2.85  
       C″: 6.5,2.25  
       D: 6.5,2.45.  
     
     
       5. Steel material according to  claim 2 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area A, B″, C′″, D′, A in the coordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       A: 9,3.1  
       B″: 9,2.85  
       C′″: 7.5,2.5  
       D′: 7.5,2.7.  
     
     
       6. Steel material according to  claim 2 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area A, B′, C′, C″, C′″, D′, A, in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       A: 9,3.1  
       B′: 9,2.65  
       C′: 6.5,2.1  
       C″: 6.5,2.25  
       C′″: 7.5,2.5  
       D′: 7.5,2.7.  
     
     
       7. Steel material according to  claim 2 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area B″, B′, C′, C″, B″ in the coordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       B″: 9,2.85  
       B′: 9,2.65  
       C′: 6.5,2.1  
       C″: 6.5,2.25.  
     
     
       8. Steel material according to  claim 2 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area D′, C′″, C″, D, D′ in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       D′: 7.5,2.7  
       C′″: 7.5,2.5  
       C″: 6.5,2.25  
       D: 6.5,2.45.  
     
     
       9. Steel material according to  claim 2 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area B″, E, F, B′, B″ in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       B″: 9,2.85  
       E: 15,4.3  
       F: 15,3.75  
       B′: 9,2.65.  
     
     
       10. Steel material according to  claim 9 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area B″, E″, F″, B′, B″ in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       B″: 9,2.85  
       E″: 11,3.35  
       F″: 11,3.05  
       B′: 9,2.65.  
     
     
       11. Steel material according to  claim 9 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area E″, E′, F′, F″, E″ in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are E″: 11,3.35 
       E′: 13,3.83  
       F′: 13,3.4  
       F″: 11,3.05.  
     
     
       12. Steel material according to  claim 9 , characterised in that the contents of on one hand carbon+nitrogen and on the other hand vanadium and any possibly existing niobium are balanced relative to each other, such that the contents of said elements will lie within the area E′, E, F, F′, E′ in the co-ordinate system in FIG. 2, where V+2 Nb,C+N-co-ordinates for said points are 
       E′: 13,3.83  
       E: 15,4.3  
       F: 15,4.0  
       F′: 13,3.4.  
     
     
       13. Steel material according to  claim 1 , characterised in that the steel contains at least 6% chromium. 
     
     
       14. Steel material according to  claim 13 , characterised in that the steel contains less than 8% chromium. 
     
     
       15. Steel material according to  claim 1 , characterised in that the steel contains 2.1-2.8% molybdenum. 
     
     
       16. Steel material according to  claim 1 , characterised in that it contains in weight-%: 2.55 C, 0.5-1.0 Si, 0.2-1.0 Mn, 7.0 Cr, 8.0 V, 2.3 Mo. 
     
     
       17. Steel material according to  claim 1 , characterised in that it contains in weight-%: 2.7 C, 0.5-1.0 Si, 0.2-1.0 Mn, 7.0 Cr, 8.0 V, 2.3 Mo. 
     
     
       18. Steel material according to  claim 1 , characterised in that it contains in weight-%: 2.45 C, 0.5-1.0 Si, 0.2-1.0 Mn, 7.0 Cr, 7.0 V, 2.3 Mo. 
     
     
       19. Steel material according to  claim 1 , characterised in that it contains in weight-%: 3.0 C, 0.5-1.0 Si, 0.2-1.0 Mn, 7.0 Cr, 10 V, 2.3 Mo. 
     
     
       20. Steel material according to  claim 1 , characterised in that it contains in weight-%: 3.5 C, 0.5-1.0 Si, 0.2-1.0 Mn, 7.0 Cr, 12 V, 2.3 Mo. 
     
     
       21. Steel material according to  claim 1 , characterised in that it contains in weight-%: 3.9 C, 0.5-1.0 Si, 0.2-1.0 Mn, 7.0 Cr, 14 V, 2.3 Mo. 
     
     
       22. Steel material according to  claim 1 , characterised in that at least 50 vol-% of said hard particles of MX type have sizes between 3 and 20 μm. 
     
     
       23. Method of manufacturing a steel material, characterised in that there is first produced a melt of an alloy having a chemical composition according to  claim 1 , that said melt is cast to ingots or castings, wherein the melt is caused to solidify so slowly that there is precipitated in the melt during the solidification process 10-40 vol-% of hard particles of MX type, where M is vanadium and/or niobium, preferably vanadium, and X is carbon and nitrogen, preferably essentially carbon, at least 50 vol-% of said hard particles having sizes between 3 and 20 μm. 
     
     
       24. Method according to  claim 23  for the manufacture of a steel material, characterised in that there is first produced a melt of an alloy having a chemical composition, that this melt is cast into ingots or castings, wherein the melt is caused to solidify so slowly that there is precipitated during the solidification process 10-25 vol-% of hard particles of MX type. 
     
     
       25. Method according to  claim 23  for the manufacture of a steel material, characterised in that there is first produced a melt of an alloy having a chemical composition, that this melt is cast into ingots or castings, wherein the melt is caused to solidify so slowly that there is precipitated in the melt during the solidification process 20-40 vol-% of hard particles of MX type. 
     
     
       26. Method of using a steel material according to  claim 1  for the manufacture of cold work tools. 
     
     
       27. Method of using a steel material according to  claim 1  for wear parts, i.e. products that are subjected to heavy abrasive wear. 
     
     
       28. Steel material according to  claim 13 , characterised in that the steel contains at least 6.5% chromium. 
     
     
       29. Steel material according to  claim 14 , characterised in that the steel contains less than 7.5% chromium. 
     
     
       30. Steel material according to  claim 22 , characterised in that at least 50 vol-% of said hard particles of MX type have sizes between 5 and 20 μm. 
     
     
       31. Method of manufacturing a steel material according to  claim 23 , characterised in that at least 50 vol-% of said hard particles of MX type have sizes between 5 and 20 μm.